So what have you done?
What error message do you get, or do you just not get your devices detected?

You haven't given much to go on, but as a guess you have only added "dtparam=i2c_arm=on" and not "dtparam=i2c_vc=on" to /boot/config.txt. i2c-0 is normally reserved for use by the GPU (VideoCore or vc) to talk to the camera and display, but if you're not using those then can be safely used from the ARM.

The default pinmuxing for i2c-0 is for GPIOs 0&1. To alter that to use the "i2c0-bcm2708" overlay with "dtoverlay=i2c0-bcm2708,pins_28_29=1".

By the way, where exactly do you get this information? Is there a manual or guide that thoroughly explains all of this? I assume you didn't just pull this out of thin air. However, I don't see it mentioned in any of the few rpi books I have.

Then I need to actually use I/o 28-SDA0, 29-SCL0, (rather than gpio 0/1) so I also added:
dtoverlay=i2c0-bcm2708,pins_28_29=1 not sure if it needs to occur before or after the previous addition, or if location matters at all.

In any case, the chip does NOT work on 28/29 (I did add 2.9K pullups from pins to 3.3V & verified).
Adding the dtoverlay=i2c0-bcm2708,pins_28_29=1 does have some effect, since when I add it gpio0 & 1 no longer work for i2c0 (and work again when I remove dtoverlay=i2c0-bcm2708,pins_28_29=1)

I've tested adding "dtoverlay=i2c0-bcm2708,pins_28_29=1" on a 3B+ and it does set up the pin muxing correctly. Use "raspi-gpio get" to print out the full config. Only one GPIO should have function SDA0, and one should have SCL0. Having multiple GPIOs with the same alt function allocated will cause issues.

You're on a Compute Module but have designed your own carrier. Have you actually provided a 3.3V supply to GPIO28-45 VDD? Pins 41&42 on the SODIMM. Use raspi-gpio again to set 28 & 29 as outputs and drive them high and low ("raspi-gpio help" to find out how to do that). What voltage do you get on the pins?

I see there is a file "dt-blob.bin" in /boot....I assume it was put there by the installation, since I don't (yet) know anything about a "blob" ...I need to study your good link. Is this something that was automatically set up? Note the only display I'm using is an HDMI display.

Should I delete this blob file? I don't need any special config, that I know of (of course, what is considered special).
=================ACTUALLY...I remember a few days ago, someone suggested I go to this page:
Re: CM3 and i2c0
Tue Aug 07, 2018 10:09 am

sudo i2cdetect -y 1 shows dashes & anything connected to i2c bus 1
================
This was vague & lousy advice, since they should have simply said:
You need to add dtparm=i2c_vc=on, rather than messing with a "blob"